1. Field of the Invention
The present invention relates to a method for greatly reducing the amount of water used in a cation exchange resin treatment for the separation of a basic amino acid from its fermentation broth.
2. Description of the Prior Art
Basic amino acids are widely used as feedstuffs and medicines, for example. At present, basic amino acids are mainly produced by fermentation, and cation exchange resins are generally utilized for separating basic amino acids from their fermentation broths. This cation exchange resin treatment generally entails an adsorption step in which a fermentation broth adjusted to a definite pH is brought into contact with strongly acidic salt-type cation exchange resins such as NH.sub.4.sup.+ -type one to adsorb the basic amino acid thereonto and, an elution step in which the basic amino acid is eluted with an eluting agent such as ammonia water, and a regeneration step wherein the cation exchange resin is regenerated to salt type one. By repeating the adsorption and elution steps as one cycle, basic amino acids are separated from their fermentation broths.
One of the problems of using the cation exchange resin treatment is that a very large quantity of water is required. In particular, a fermentation broth is passed through a cation exchange resin layer and then a washing water feed is employed in order to completely pass the fermentation broth through the cation exchange resin layer at the adsorption step. Further, at the elution step, a washing water feed is employed in order to completely pass the eluting agent. Additionally, suspensions and the like, contained in the fermentation broth, accumulate in the cation exchange resin layer at the adsorption step, and a large quantity of water must be used to remove the accumulated solid. Hence, there are problems relating not only to the amount of water consumed but also to the increased amount of waste water discharged.
Various methods for reducing the amount of washing water used have been investigated and, some methods for substituting various waste liquids for a part of this washing water have been developed (Japanese Unexamined Patent Publications No. 127879/75, 11173/77, etc.). However, due to mixing with liquids used in subsequent steps or the loss of basic amino acids in elution by washing water, which occur in these methods, a considerable quantity of fresh washing water must still be used.
Moreover, the concentration of the basic amino acids in the eluate discharged from the cation exchange resin is low and, therefore, much energy is required for concentrating the eluate.
Therefore, a need clearly continues to exist for a method for separating a basic amino acid from its fermentation broth, or the liquids resulting from the intermediate treatment of the fermentation broth, containing high-molecular weight contaminants, using a cation exchange resin, which utilizes a greatly reduced amount of water, and which, therefore, also requires the use of less energy in concentrating large quantities of eluate.